1. Field of the Invention
The invention relates to a mobile route-monitoring unit, to be used in particular in a truck.
2. Discussion of the Background
Every shipping company is faced with the problem of comparing the current location of its trucks and their cargoes with a planned route and schedule. The foregoing is necessary to identify any tardiness or theft/seizure as early as possible.
Previously, this problem was successfully solved by a transmission unit installed in the truck sending current location information to the control room at certain time or distance intervals determined by a GPS receiver or a gyrosensor. The previous method for transmitting information was using a mobile phone network Short Message Service, because the costs of sending messages via SMS are substantially lower than voice mobile communications. The position message was processed at the control room and compared with the planned route and time data, which in the event of a route deviation set off an alarm.
Frequently, an “authorized area” system is used to define a route deviation; in this system the planned route is represented as a series of consecutive ellipses, which cover the planned route plus minor lateral deviations. Staying outside the “authorized” consecutive ellipses is considered a route deviation. An example of this type of route representation is shown in FIG. 3.
FIG. 3 shows a route 1 and a number of ellipses 10 which cover the route and taken together establish an ample “authorized route corridor.” Typically, the traveled route is measured using an odometer in the truck and a position message is sent to the control room via SMS service, for example every 10 km. Such messages are represented in the figure by message points 9A, 9B and 9C.
This type of system has many disadvantages. For example, the truck has to send confirmation signals at regular intervals, which results in high costs. This is especially true for foreign travel, because SMS messages cost significantly more abroad than domestically. That explains why the intervals between confirmation signals tend to be large. Which in turn leads to a substantial increase in the size of the probable location at any given moment. This problem is also shown schematically in FIG. 3: Circle 11. Circle 11 has a radius r, of, for example, 10 km, at message point 9B. The shaded area of Circle 11 therefore represents the “unauthorized” area in which a vehicle can be located which is moving along the route on schedule at message point 9B. In general, a route representation using “authorized” elliptical areas produces an uneven route corridor that allows and/or prohibits widely divergent deviations. In FIG. 3, for example, the authorized deviation A from message point 9A to the west (in FIG. 3 north is indicated using the usual cartographic convention) is substantially smaller than the authorized deviation B from message point 8A to the east.
The fact that SMS service is currently available in about only 40% of Europe results in an additional, considerable limitation to the possibility of monitoring.